The invention concerns a method as an apparatus for threading the end of a wrapper web from a wrapper roll into a nip between wrapper proportioning drawing rolls.
Getting a modern wrapping machine and roll wrapping device ready for operation usually requires the input of at least two operators. Using older equipment, getting it ready for operation and changing the wrapper rolls can be even harder. One of the most time-consuming and care-requiring tasks is the threading of the wrapper web from a new roll brought to the wrapping device into the nip between the wrapper proportioning drawing rolls. The wrapper has to remain straight during the feeding and the nip between the drawing rolls has to be closed in such way that both edges of the wrapper are of the same length between the roll and the drawing roll nip. In this way a uniform transverse tension of the wrapper is achieved. Since the positions of the wrapper roll and the drawing roll are invariable with respect to each other, a wrapper that has been positioned askew cannot straighten out in the drawing roll nip, except by wrinkling before the drawing roll nip, and the wrinkle goes through the nip. Further, if the transverse tension of the wrapper is not uniform, the tension of the wrapper that is to be wrapped around a roll will become nonuniform and the wrapping quality will suffer, because a loose wrapper layer will not support the roll sufficiently. A uniform wrapper tension is of particular significance to the quality of the wrapping in the so-called multiple wrapping, where several parallel rounds of wrapper are wrapped around a roll.
The object of the present invention is to provide a method and apparatus for threading a wrapper automatically and reliably from the wrapper roll to the nip between the wrapper proportioning drawing rolls. A prepared roll positioned ready for use is rotated against the feeding direction, whereupon the free wrapper end arrives on the wrapper feeding table and can be detected. When the wrapper end has been detected, the direction of rotation of the wrapper roll is changed and the wrapper is advantageously fed by blowing air to the nip between the drawing rolls and the nip is closed.
Considerable advantages are achieved by means of the present invention.
The most significant advantage of the invention is that the end of the wrapper can be threaded to the drawing roll nip automatically and very reliably. The wrapper does not need to be threaded by hand at any stage and the wrapper is always guided by the machine straight forward, whereupon the wrapper arrives straight to the drawing roll nip and its transverse tension will become uniform when the drawing roll nip is closed. Due to the automatic and reliable guiding the number of possibilities for errors in connection with the changing of wrapper rolls will decrease, by which the quality and reliability of the functioning of the entire wrapping system can be influenced. This makes the work of the wrapping machine operators easier, enabling them to concentrate on the matters that are the most essential ones for the functioning of the system and on the quality control of the rolls that are to be wrapped.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are intended solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims.